zhertec

This is probably a pretty noob question, but what am I doing wrong?

I've tried stabilised idle hunting by making the idle VE cells the same (which works perfectly during warmup), but when the car is completely off ASE and WUE, AFR progressively hunts and creeps slowly towards leaning out. One thing I've noticed is that every few engine cycles it will lean out severely (and idle will drop) but quickly recover (misfire?).
I thought it would be a timing/spark issue but timing is dead on 10 degrees when changed to fixed, and all plugs are gapped to around 0.038-44" and are relatively new.
I've tried bumping up the VE table, but with NB's returnless fuel rail and heatsoaking injectors, this is proving to be very annoying.

Note: In the second start, fuel around idle is bumped to ~110-120 since it began to lean out.

Also can moderators please delete my other post as tune and datalog was kinda all over the place: https://www.miataturbo.net/ecus-tuni...m-idle-101165/

EDIT: 1998/9 mx5 base model, all stock (using stock iat), no issues on standard ecu.

zhertec

So I just went out and did a quick timing light check on all cylinders to check if they were firing properly, turns out cyl 4 is firing erratically i.e. sometimes slows down and speeds up, compared to cyl 1-3 which all give off stable pulses of light.
Since 1 & 4, 2 & 3 are fired together I'm assuming this issue is related to either my ignition coils or crappy leads am I correct?

der_vierte

Plugs or wires, yes... known miata problem

zhertec

*sigh* Changed them only a year ago. Guess it's time to do it again and see if it fixes the problem...

curly

iTrader: (25)

Yes, change the plugs and wires, and if you haven't in the last 6 minutes, change your NB1 coils. You've also got nothing correcting fueling, and nothing to stabilize the idle. I've enabled EGO control and idle advance in the attached tune, try it out, it should stay much more stable.

zhertec

Just to update, swap the plug lead positions of 1 and 4 on the coil and the problem moved to cyl 1, so I'm guessing I need a new coil pack .
And I turned ego correction off initially cause I read you should have a somewhat steady idle on complete open loop before moving on the closed loop, but thank you for the tune!
I'll give another update after I swap the coils out.

der_vierte

Maybe go COP's right away?

zhertec

I was thinking ls2 coils instead hahaha, do it once so I won't have to upgrade when I turbo.
I also found this misfiring issue is appearing on cyl 2...damn

der_vierte

There's no question what to do now...

zhertec

Ok, LS d585 coils have been installed (flowforce pnp kit) and the timing light issue has disappeared (spark plugs are still the same though fairly ok ~10,000 km), but there is still a misfire of some sort? Even with ego control and idle advance I still get erratic afr and idle hunting :(

I notice this issue comes intermittently during warm up (as seen from the afr lean spikes and recovery), but gets progressively worse with increase in CLT

irollgen4s

I don't have a log viewer on this computer so im speculating purely based off of my experience.

Any chance its hitting fuel cut when it spikes lean? Check overrun fuel cut min map setting. That was an issue a long time for me on idle being inconsistent and unstable similar to what you are experiencing

Also use open loop idle instead of closed loop idle it seems a lot more consistent at least in my experience.

zhertec

I believe I've turned off all types of fuel cut possible, there's still PW signal when it spikes lean (which I assume means it's still injecting fuel), though it does increase whenever afr has a lean spike, probably due to the closed loop nature? i.e. trying to make it richer.

I've attempted to use pure open loop, but the problem still persists. Since I haven't known how long the coil pack has been dead (98 nb no CEL), I'll do a precautionary change on the possibly fouled spark plugs and report back.

Thanks for all the input btw

zhertec

New spark plugs helped a tad, but the misfire still occurs at coolant temps above 80 degrees, and gets progressively worse the warmer the engine is. Also did a quick compression test, which showed pretty similar values for all cyl (very slightly lower on cyl 4, but within 10-20 psi).
Next step I guess is to pull the board and see if all the connections are solid and in the right place...

zhertec

Heres the board, anything blaringly wrong? I have 0 electrical experience so ...

curly

iTrader: (25)

Sure you’re not just triggering AE?

zhertec

AE is off in the tune and from the logs I think they're always at 100%.
The fact that the car works quite on a half dead coil pack suggests it shouldn't be a physical fault with the car right?
So it must be either a ms communication issue or something...

Also quick question, I'm pretty sure aftermarket alarms/immobilisers can't cut spark or fuel right? Or if they can, it would be immediate and the car wouldn't idle at all yea?

StanTheMan

For years I had this shitty old alarm & central locking causing a little bit of grief....like the hazards would start. I'd stick my hand under the dash move the wiring, reset the alarm & off I'd go. every time i had any electrical issues the first thing I'd suspect is that shitty alarm & wiring under my dash. It proved never to be the case. recently a sparky friend of mine un attached the whole system.. bliss. My alarm had fuel cut...but it hasn't worked in years. LMAO


but the point is its probably unlikely your alarm is causing an intermittent fault.

& if you seriously suspect the alarm being the cause.....you don't want it to be in your car. Get rid of it.

hks_kansei

They can cut either, or both.
really depends on the alarm.

Most alarms are garbage anyway, a decent car thief will have them bypassed in a few seconds.

zhertec

Alright so as annoying as that thing is, I'll leave it alone for now (wiring is a freaking mess for it).
I've noticed from before and after LS coils in the logs that the misfiring became worse after upgrading (more rapid distinct spikes), which points to a spark issue. I'll check my ecu grounds and wiring and see if gets any better...

zhertec

After doing a bit more reading (https://www.miataturbo.net/mspnp-55/...issions-62233/) it's suggested to adjust timing to 10 degrees (for NA miata though...should it matter much?), rather than have the basemap of 15+ at idle, should I scale down the timing map to achieve this? Or just throw in 10 degrees in the idle cells and interpolate around it?